There are several methods which can be applied in order to test the propagation speed of nerve impulses through the motor fibers by evaluating the lag period in the appearance of motor-reaction in the successive stimulations performed at different levels on a motor-nerve tract. It is also known to evaluate the propagation velocity of nerve impulses through the sensitive nerve fibers by recording the working current induced by a single distal excitation of sensitive nerve endings, at two different levels on a peripheral nerve tract. These methods are currently applied in neurological investigations.
It is also known that electrodermal reflexes appear -- with an increasing latency -- in intense fatique states under stress conditions, under diffuse hyperexcitation of nervous system as well as in nerve intoxication. The vegetative nervous fibers exhibit an increased sensitivity to the absence of oxygen and to the action of carbon dioxide and certain nerve toxins.
Evaluation of an increased latency of electrodermal reflexes in all the above-mentioned cases requires the limitation of central nervous disorders comparative to peripheral disorders. On the other hand, the decrease of nerve-impulse-propagation velocity through the peripheral vegetative fibers is an important factor in nervous disorders. The increase or decrease in nerve-impulse-propagation velocity evidences a series of pathological or physiological states. Such as hyperexcitation or fatigue, having one common characteristic, i.e. the increase in the latency of electrodermal reflexes.